US5287854A - Electron spin resonance enhanced MRI using an echo planar imaging technique - Google Patents
Electron spin resonance enhanced MRI using an echo planar imaging technique Download PDFInfo
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- US5287854A US5287854A US07/768,202 US76820291A US5287854A US 5287854 A US5287854 A US 5287854A US 76820291 A US76820291 A US 76820291A US 5287854 A US5287854 A US 5287854A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
- G01R33/5615—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/62—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using double resonance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/561—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
- G01R33/5615—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
- G01R33/5616—Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE] using gradient refocusing, e.g. EPI
Definitions
- the present invention relates to improvements in and relating to magnetic resonance imaging (MRI) and in particular to apparatus for and methods of electron spin resonance enhanced magnetic resonance imaging (ESREMRI).
- MRI magnetic resonance imaging
- ESREMRI electron spin resonance enhanced magnetic resonance imaging
- ESREMRI is a method of magnetic resonance imaging in which amplification of the nuclear magnetic resonance signal, the free induction decay (FID) signal, is achieved by stimulating an electron spin resonance transition of a paramagnetic species present in the subject being imaged. Stimulation of the ESR transition leads to a polarization of the nuclear spin system responsible for the FID signals from which the magnetic resonance (MR) image of the subject is generated.
- This so called dynamic nuclear polarization is in effect an overpopulation, relative to equilibrium values, of the excited nuclear spin state and can be so large that the FID signal may be amplified by a factor of well over 100.
- MR images may be generated by conventional imaging procedures, such as for example two and three dimensional Fourier transform, with enhanced signal to noise (SN) ratios (due to the amplification of the FID signal) and/or with shorter image acquisition times (since the nuclear spin system does not have to be allowed to relax towards equilibrium over a period comparable with T 1 , the spin-lattice relaxation time, for example about 1 second, between each excitation /FID signal detection cycle) and/or at lower strength primary magnetic fields than are conventionally utilized in MRI, e.g. 0.002 to 0.1 T or lower.
- SN signal to noise
- ESREMRI involves exposing the subject being imaged to pulses of electromagnetic radiation of frequencies selected such that ESR and NMR transitions are stimulated.
- the ESR and NMR stimulating radiations are generally microwave (MW) and radiofrequency (RF) radiations, for the sake of convenience the ESR and NMR stimulating radiations will be referred to hereinafter as being MW and RF radiations respectively.
- the ESR transition(s) of the paramagnetic species which may be naturally present in the subject being imaged but more generally will be administered to the subject as a contrast agent, should be stimulated at or near saturation level for a period leading up to the initial RF pulse of the RF pulse/FID signal detection cycle of the MR image acquisition procedure.
- Exposure of live subjects to electromagnetic radiation of RF or MW frequencies may cause undesirable heating of the subject's tissues to occur and clearly it is essential for a diagnostic technique such as MRI (and ESREMRI) that the temperature increases in the tissue be kept down to an acceptable level.
- the maximum radiation exposure should be about 1-8 W/kg bodyweight during the imaging procedure. If MRI is conducted in accordance with these recommendations, any tissue temperature rises should be acceptably low, e.g. less than about 1° C., even for extended imaging periods.
- ESREMRI involves exposing the subject being imaged not just to the nuclear magnetic resonance stimulating RF radiation that is conventional within MRI, but also to electron spin resonance stimulating MW radiation. Accordingly, it is particularly important in in vivo ESREMRI to avoid undue exposure of the subject to MW radiation whereby to avoid undue heating of the subject's tissues.
- any paramagnetic contrast agent used as the source of the MW stimulated ESR transitions should have an ESR spectrum in which the stimulated transition(s) should have a linewidth of less than 1 gauss.
- the paramagnetic metal compounds, e.g. chelates, salts, etc. that have been found in conventional MRI to be effective T 1 contrast agents.
- EP-A-296833 focused attention on the suitability as ESREMRI contrast agents of various stable free radicals, such as for example nitroxides.
- nitroxide stable free radicals which have ESR linewidths of less than 1 gauss generally are less efficient as T 1 contrast agents in MRI--more specifically they generally have lower relaxivities or specific relaxation rate (1/T 1 ) enhancement values than do the paramagnetic metal species--containing T 1 contrast agents. Accordingly, up to now, choice of ESREMRI as an imaging technique has meant that a relatively low relaxivity contrast agent had to be used and that contrast agent dosages have had to be relatively high.
- ESREMRI Echo Planar Imaging
- Mansfield P J.Phys.C.10:L55-58 (1977)
- the new technique according to the invention moreover represents an improvement in the performance of EPI since ESREMRI may be performed using primary magnetic fields lower in field strength than those primary fields generally used in MRI and may thus benefit from all the advantages of operating at lower primary field strengths.
- Rapid magnetic field changes are considered undesirable for live subjects, but by operating at the low primary field strengths of for example 500 gauss or below, especially 200 gauss or below, that are utilizable for ESREMRI, smaller magnitude magnetic field gradients than are conventional in MRI may be used and as a result the magnetic field variation dG/dt in EPI may be reduced, or the FID signal utilization may be enhanced by switching the gradient polarity more rapidly.
- the present invention provides a method of electron spin resonance enhanced magnetic resonance imaging characterized in that imaging is performed by an echo planar imaging technique.
- the present invention provides a method of electron spin resonance enhanced magnetic resonance imaging of a human or non-human animal subject, wherein free induction decay signal detection is effected during imposition of a magnetic field read gradient across said subject, characterized in that the polarity of said read gradient is repeatedly inverted.
- the method of the invention may thus for example comprise the following steps:
- step (b) of the method of the invention may be performed using extremely low field strength primary magnets or even using the earth's ambient magnetic field as the primary magnetic field.
- Low field operation of ESREMRI is discussed in EP-A-296833 and in WO-A-90/02345 (Leunbach).
- the dynamic nuclear polarization step, step (c), should precede, but may overlap with, the initial pulse of RF radiation of the RF excitation/FID signal detection cycle. Any delay between termination of the MW pulse and commencement of the RF pulse should preferably be avoided or kept to a minimum.
- successive gradient pulses may if desired vary in magnitude and/or duration.
- the time variation of the read gradient (e.g. Gx), and indeed of the other magnetic field gradients, in the method of the present invention may be in any manner suitable for use in any version of Echo Planar Imaging.
- Gx may simply be repeatedly reversed in polarity or, more preferably, it may continuously vary, e.g. approximately sinusoidally, or it may be discontinuous, e.g. occuring as discrete blips of alternating polarities.
- the literature regarding EPI is extensive and the reader is referred particularly to the publications of Mansfield and Rzedzian and their co-workers. Particular attention in this regard is drawn to EP-A-270320 (Rzedzian), U.S. application 4628264 (Rzedzian), U.S.
- two dimensional Fourier transform for example, spatial information is encoded into the FID signal by imposing a series of magnetic field gradients on the primary magnetic field, e.g. by imposing gradients in the x, y and z directions, at different stages of the RF excitation/FID signal detection cycle.
- a gradient the read gradient, is imposed during the period when FID signal detection occurs. This however causes the FID signal to decay much more rapidly than it would in the absence of the read gradient and indeed the FID signals generally are only strong enough to be readily detected for periods of the order of 10 -4 sec, even though T 2 in the body may be of the order of 2-20 ⁇ 10 -2 sec.
- the FID signal envelope resembles a sinc function and generally first passes through zero at about 10 microseconds.
- the EPI technique involves repeatedly reversing the polarity of the read gradient so that its dephasing effect is reversed and the FID signal builds back up again.
- the characteristic decay time for the overall envelope of the FID signal thus becomes T.sub. 2 * and the FID signal is thus much more efficiently utilized.
- Gradient reversal if effected after the FID signal has died out, will result in an "echo" signal developing.
- gradient reversal is effected before the FID signal has died out, e.g. at a rate of about 10 kHz, signal intensity will build up again before it has completely decayed.
- the gradient across each volume element must also be comparable to, if not larger than, the intrinsic inhomogeneities of the primary magnetic field, e.g. inhomogeneities due to imperfections in coil winding and geometries and/or variations in current in the magnet's coils.
- the FID signal enhancement which can be over a hundred fold, which results from the use of the ESREMRI technique allows satisfactory SN ratio FID signals to be detected even at extremely low strength primary magnetic fields. Accordingly, the combination of ESREMRI and EPI may allow the use in EPI of lower strength primary magnetic fields and hence of higher frequency read gradient reversal, of lower magnitude read gradients and of higher inhomogeneity (and hence less expensive) magnets.
- the primary field strength is less than 1T, preferably less than 0.8T, especially preferably less than 0.1T, more preferably less than 0.08T (800 gauss) and particularly preferably 200 gauss or less, e.g. 20 to 200 gauss.
- Ne 1/2 the order of the order of Ne 1/2 (where Ne is the number of reversals, assuming Ne ⁇ 2 ⁇ is less than or much less than T 2 where 2 ⁇ is the spacing of the FID echoes).
- Ne the number of reversals, assuming Ne ⁇ 2 ⁇ is less than or much less than T 2 where 2 ⁇ is the spacing of the FID echoes.
- EPI could be used simply as a modification of a conventional MR imaging procedure such as 2-dimensional Fourier transform, etc.
- the EPI technique thus affords the opportunity to reduce the total MW exposure of the subject by reducing the number of RF excitation/FID signal detection cycles and thus the number of MW exposure periods required for the acquisition of a single image.
- the method of the present invention will be a so-called single shot imaging procedure requiring only one period during which the subject is exposed to MW radiation in order to generate the desired dynamic nuclear polarization within the nuclear spin system of the nuclei responsible for the detected FID signals. During this period MW exposure may be continuous or discontinuous.
- the EPI technique can be used to reduce the number of MW exposure periods for each image acquisition period, higher MW exposure during the (or each) MW exposure period can be tolerated. This is especially true for single shot imaging according to the method of the invention in which image generation requires the subject to be exposed to MW radiation during only one dynamic nuclear polarization (DNP) generation period, generally 10 to 10 5 ms, preferably 200 to 10 4 ms, especially preferably 500 to 2000 ms.
- DNP dynamic nuclear polarization
- paramagnetic contrast agents species having ESR linewidths of up to 2 gauss, e.g. from 0.01 to 2 gauss, preferably up to 1.5 gauss, especially preferably between 1.0 and 1.5 gauss.
- the range of paramagnetic species utilizable as ESREMRI contrast agents is significantly extended by the present invention and, while the linewidths of conventionally preferred gadolinium containing MRI T 1 contrast agents, such as Gd DTPA, Gd-DTPA-Bismethylamide, GA DOTA, Gd DO3A etc, will still be too large for these compounds to function effectively as ESREMRI FID signal enhancing contrast agents, the present invention makes it possible to use certain relatively narrow ESR transition linewidth materials as ESREMRI FID signal enhancing contrast agents.
- the present invention provides a contrast medium for use in FID signal enhancing in the ESREMRI methods of the invention, said contrast medium comprising a physiologically tolerable paramagnetic material having in its ESR spectrum a transition having a linewidth of between 1 and 2 gauss, together with at least one carrier or excipient.
- the invention also provides the use of such paramagnetic materials for the preparation of a diagnostic agent for use in a method of ESREMRI imaging of a human or non-human animal subject.
- one of the most significant benefits of the method of the invention is that it permits use in ESREMRI of high relaxivity paramagnetic materials as FID signal enhancing contrast agents.
- Increased relaxivity although generally associated with increased ESR linewidth, is desirable since it means that the efficiency of the contrast agent in terms of required dosage is also increased.
- paramagnetic materials having a quality factor (Q) of at least 1, preferably at least 1.3, especially preferably at least 1.4, where Q is defined as follows
- R 1 is the T 1 relaxivity in mM -1 s -1 and LW is the ESR transition linewidth in gauss.
- relaxivity may be measured as the regression coefficient or gradient B in the equation
- x is the concentration in mM of the paramagnetic species and y is 1/T 10 (in sec -1 -T 10 is the spin-lattice relaxation tissue T 1 for the solution containing the paramagnetic species) and A is the value of 1/T 1 (in sec -1 ) in the absence of the paramagnetic species (e.g. in a reference water/glycerol mixture (17:8 by volume) at 37° C.).
- the invention provides a diagnostic composition for use in the ESREMRI methods of the invention, said composition comprising a physiologically tolerable paramagnetic material having a quality factor of at least 1, preferably at least 1.5, together with at least one physiologically tolerable carrier or excipient.
- the ESR linewidths referred to herein are the full widths at half maximum in the absorption spectrum at imaging conditions, e.g. at the imaged sites. Particularly, preferably however the linewidth criteria will be satisfied at the local concentration limits mentioned below.
- the contrast medium may contain, besides the paramagnetic material, formulation aids such as are conventional for therapeutic and diagnostic compositions in human or veterinary medicine.
- the agents may for example include solubilizing agents, emulsifiers, viscosity enhancers, buffers, etc.
- the agents may be in forms suitable for parenteral (e.g. intravenous) or enteral (e.g. oral) application, for example for application directly into body cavities having external escape ducts (such as the digestive tract, the bladder and the uterus), or for injection or infusion into the cardiovascular system.
- parenteral e.g. intravenous
- enteral e.g. oral
- solutions, suspensions and dispersions in physiologically tolerable media will generally be preferred.
- the contrast medium which preferably will be substantially isotonic, may conveniently be administered at a concentration sufficient to yield a 1 micromolar to 10 mM concentration of the paramagnetic substance at the image zone; however the precise concentration and dosage will of course depend upon a range of factors such as toxicity, the organ targetting ability of the contrast agent, and administration route.
- the optimum concentration for the paramagnetic substance represents a balance between various factors. In general, operating with a primary magnet generating a 0.02 T field, optimum concentrations may lie in the range 1 to 10 mM, especially 3 to 9 mM, more especially 4 to 8 mM and particularly 4.5 to 6.5 mM.
- compositions for intravenous administration preferably will contain the paramagnetic material at concentrations of 10 to 1000 mM, especially preferably 50 to 500 mM.
- concentrations for imaging of the urinary tract or the renal system however compositions may perhaps be used having concentrations of for example 10 to 200 mM.
- concentration may conveniently be 1 to 10 mM, preferably 3 to 9 mM etc.
- the invention provides a contrast medium for use in the ESREMRI methods of the invention, said contrast medium comprising a physiologically tolerable paramagnetic material, e.g. a stable free radical, e.g. a nitroxide, at a concentration of from 50 to 500 mM in a sterile physiologically tolerable liquid carrier, said paramagnetic material having an ESR transition with a linewidth of at least 1 gauss and up to 2 gauss, preferably up to 1.5 gauss, especially preferably from 1.2 to 1.5 gauss.
- a physiologically tolerable paramagnetic material e.g. a stable free radical, e.g. a nitroxide
- the paramagnetic material in the contrast media of the invention will preferably exhibit ESR linewidths of less than 2 gauss, especially preferably less than 1.5 gauss, at concentrations of up to 10 mM, especially at 1 or 2 mM, or even somewhat higher.
- the prior art ESREMRI contrast media e.g. those described in EP-A-296833, may of course be used in the method of the present invention.
- the invention also provides a magnetic resonance imager arranged for performing ESREMRI, comprising gradient imposing means for imposing at least one magnetic field gradient across a sample in said imager, detection means for detecting FID signals from a said sample, first control means for controlling said gradient imposing means, and second control means for controlling the operation of said detection means, characterized in that said first control means is arranged to impose across a said sample magnetic field read gradients of alternating polarities and in that said second control means is arranged to cause said detection means to operate during at least part of the time during which said read gradients are imposed.
- the control means in the apparatus of the invention preferably comprises a computer, which may function as both the first and the second control means.
- this control means will also serve to control the imposition of the other field gradients and especially preferably also the MW and RF sources, e.g. to select the frequency bandwidths and central frequencies of the MW and RF pulses emitted during the image acquisition procedure.
- the computer will preferably be arranged for manipulation of the detected FID signals to generate one or more MR images of the subject.
- the method of the invention is particularly suited to the imaging of samples of relatively small diameter (e.g. laboratory animals, limbs and other subjects for which a sample aperture diameter in the imaging apparatus of up to 20 cm, and preferably up to 10 cm, will suffice) and for the study of dynamic rather than static systems where the relative importance of temporal rather than spatial resolution increased.
- samples of relatively small diameter e.g. laboratory animals, limbs and other subjects for which a sample aperture diameter in the imaging apparatus of up to 20 cm, and preferably up to 10 cm, will suffice
- FIG. 1 is a schematic diagram of an ESREMRI imager according to the invention.
- FIGS. 2 and 3 are schematic diagrams of the timing sequences for MW and RF pulses, read gradient imposition, FID signals and FID signal detection in single shot imaging procedures effected according to the method of the present invention.
- an ESREMRI apparatus 1 having a subject 2, dosed with a paramagnetic contrast agent (e.g. a 30 g mouse dosed with 0.5 mmol/kg of a paramagnetic contrast agent, e.g. PROXYL D, PROXYL H, 4-amino-TEMPO, TEMPOL or another commercially available nitroxide stable free radical), placed at the axis of the coils of electromagnet 3.
- a paramagnetic contrast agent e.g. a 30 g mouse dosed with 0.5 mmol/kg of a paramagnetic contrast agent, e.g. PROXYL D, PROXYL H, 4-amino-TEMPO, TEMPOL or another commercially available nitroxide stable free radical
- Power from DC supply 4 to electromagnet 3 enables the primary magnetic field, e.g. a 200 gauss field, to be generated.
- the apparatus is further provided with resonators 5 and 6 for emitting the second (RF) and first (MW) radiations respectively.
- Resonator 5 is connected to RF transceiver 7 powered by power supply 8 and resonator 6 is connected, for example by waveguides, to microwave generator 9 which is powered by power supply 10.
- the resonators, especially resonator 6, may be so-called loop-gap resonators.
- Microwave generator 9 may be arranged to emit MW radiation having more than one maximum frequency in order to excite more than one esr transition.
- the frequency selection, bandwidth, pulse duration and pulse timing of the second and first radiations emitted by resonators 5 and 6 are controlled by control computer 11 and interface module 18.
- Computer 11 also controls the power supply from power sources 12, 13 and 14 to the three pairs of Helmholtz coils 15, 16 and 17.
- the coils of coil pair 15 are coaxial with the coils of electromagnet 3 and the saddle coils of coil pairs 16 and 17 are arranged symmetrically about that axis, the Z axis, with their own axes mutually perpendicular and perpendicular to the Z axis.
- Coil pairs 15, 16 and 17 are used to generate the magnetic field gradients that are superimposed on the main field at various stages of the imaging procedure and the timing sequence for operation of the coil pairs and for operation of the MW generator and the RF transceiver is controlled by computer 11 and interface module 18.
- the apparatus may also be provided with decoupler comprising a further RF resonator 19 (shown with broken lines) connected to an RF transmitter and a power supply (not shown) and controlled by computer 11.
- the decoupler may be operated to emit a third radiation at a frequency selected excite the nuclear spin transition in non-zero spin nuclei in the contrast agent.
- the power supply to the electromagnet 3 is switched on and an essentially uniform main magnetic field is generated within the cavity within its coils.
- the magnitude of the main field generated by electromagnet 3 is maintained essentially constant throughout the imaging procedure.
- the subject 2 for example a patient, is placed within the coil cavity and after a short delay, for example several seconds, the imaging procedure can begin.
- the imaging procedure used e.g. the sequence of exposure of subject 2 to RF radiation from resonator 5, imposition of field gradients by coil pairs 15, 16 and 17 and detection of the FID signal by transceiver 7 may be substantially as in any conventional EPI technique (e.g. as described in the Mansfield and Rzedzian references mentioned above) with the inclusion of a period of DNP generating MW exposure at the beginning of the or each RF excitation/FID signal detection cycle.
- EPI technique e.g. as described in the Mansfield and Rzedzian references mentioned above
- the degree of DNP (P ex -P gs )/(P gs -P ex ) where P ex and P gs are the excited and ground nuclear spin state populations and P gs and P ex are the ground and excited nuclear spin state populations at thermal equilibrium.
- timing sequences for single shot imaging are shown schematically in FIGS. 2 and 3.
- the read gradient reversal rate is sufficiently slow, e.g. 0.5 ms between reversals, that the FID signal decays completely between reversals and reappears as an echo after reversal.
- read gradient reversal is effected very rapidly, e.g. with 50 microseconds between reversals, so that the signal does not decay completely between reversals.
- Phase encoding (Gv) and slice selection (Gz) gradient timings are also shown schematically in FIGS. 2 and 3. It will be appreciated that, as is conventional with EPI techniques, gradient magnitudes may be varied during the gradient imposition detection sequence to enable the spatial information for the generation of a full image to be encoded into the FID signals and echoes.
Abstract
Description
Q=R.sub.1 /(LW).sup.2
y=A+Bx
Claims (11)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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GB898909270A GB8909270D0 (en) | 1989-04-24 | 1989-04-24 | Method |
GB8909270.4 | 1989-04-24 |
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US5287854A true US5287854A (en) | 1994-02-22 |
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US07/768,202 Expired - Fee Related US5287854A (en) | 1989-04-24 | 1990-04-12 | Electron spin resonance enhanced MRI using an echo planar imaging technique |
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US (1) | US5287854A (en) |
EP (1) | EP0470084B1 (en) |
JP (1) | JP2902107B2 (en) |
AT (1) | ATE108026T1 (en) |
AU (1) | AU638985B2 (en) |
CA (1) | CA2050494C (en) |
DE (1) | DE69010329T2 (en) |
GB (1) | GB8909270D0 (en) |
NO (1) | NO302447B1 (en) |
WO (1) | WO1990013047A1 (en) |
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US5755665A (en) * | 1995-03-03 | 1998-05-26 | Hitachi Medical Corporation | Apparatus and method for simultaneous detection of multiple magnetic resonance images |
US6188219B1 (en) | 1999-01-22 | 2001-02-13 | The Johns Hopkins University | Magnetic resonance imaging method and apparatus and method of calibrating the same |
US6675034B2 (en) * | 2001-04-19 | 2004-01-06 | Sunnybrook And Women's Health Sciences Centre | Magnetic resonance imaging using direct, continuous real-time imaging for motion compensation |
US20070025918A1 (en) * | 2005-07-28 | 2007-02-01 | General Electric Company | Magnetic resonance imaging (MRI) agents: water soluble carbon-13 enriched fullerene and carbon nanotubes for use with dynamic nuclear polarization |
CN109620224A (en) * | 2019-01-10 | 2019-04-16 | 哈尔滨华奥新技术开发有限公司 | Electron paramagnetic imager |
US10444312B2 (en) | 2016-05-02 | 2019-10-15 | Gachon University Of Industry-Academic Cooperation Foundation | Magnetic resonance imaging system |
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GB8929300D0 (en) * | 1989-12-29 | 1990-02-28 | Instrumentarium Corp | Apparatus |
GB9111738D0 (en) * | 1991-05-31 | 1991-07-24 | Instrumentarium Corp | Method |
GB9216597D0 (en) * | 1992-08-05 | 1992-09-16 | British Tech Group | Method of obtaining images representing the distribution of paramagnetic material in solution |
ES2175123T3 (en) * | 1995-09-08 | 2002-11-16 | Nycomed Imaging As | PROCEDURE THAT SERVES TO DETERMINE THE CONCENTRATION OF OXYGEN IN A SAMPLE. |
EP1960001A2 (en) | 2005-12-08 | 2008-08-27 | Koninklijke Philips Electronics N.V. | System and method for monitoring in vivo drug release using overhauser-enhanced nmr |
GB0920839D0 (en) * | 2009-11-27 | 2010-01-13 | Univ Bristol | Contrast agents for medical imaging |
KR101967239B1 (en) | 2012-08-22 | 2019-04-09 | 삼성전자주식회사 | Method for imaging magnetic resonance image and appratus using the same thereof |
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1989
- 1989-04-24 GB GB898909270A patent/GB8909270D0/en active Pending
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1990
- 1990-04-12 US US07/768,202 patent/US5287854A/en not_active Expired - Fee Related
- 1990-04-12 EP EP90905507A patent/EP0470084B1/en not_active Expired - Lifetime
- 1990-04-12 AU AU54099/90A patent/AU638985B2/en not_active Ceased
- 1990-04-12 DE DE69010329T patent/DE69010329T2/en not_active Expired - Fee Related
- 1990-04-12 JP JP2505628A patent/JP2902107B2/en not_active Expired - Lifetime
- 1990-04-12 CA CA002050494A patent/CA2050494C/en not_active Expired - Fee Related
- 1990-04-12 AT AT90905507T patent/ATE108026T1/en not_active IP Right Cessation
- 1990-04-12 WO PCT/EP1990/000604 patent/WO1990013047A1/en active IP Right Grant
-
1991
- 1991-10-23 NO NO914170A patent/NO302447B1/en unknown
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US5755665A (en) * | 1995-03-03 | 1998-05-26 | Hitachi Medical Corporation | Apparatus and method for simultaneous detection of multiple magnetic resonance images |
US6188219B1 (en) | 1999-01-22 | 2001-02-13 | The Johns Hopkins University | Magnetic resonance imaging method and apparatus and method of calibrating the same |
US6675034B2 (en) * | 2001-04-19 | 2004-01-06 | Sunnybrook And Women's Health Sciences Centre | Magnetic resonance imaging using direct, continuous real-time imaging for motion compensation |
US6924643B2 (en) | 2001-04-19 | 2005-08-02 | Sunnybrook And Women's College Health Sciences Centre | Magnetic resonance imaging using direct, continuous real-time imaging for motion compensation |
US20070025918A1 (en) * | 2005-07-28 | 2007-02-01 | General Electric Company | Magnetic resonance imaging (MRI) agents: water soluble carbon-13 enriched fullerene and carbon nanotubes for use with dynamic nuclear polarization |
US10444312B2 (en) | 2016-05-02 | 2019-10-15 | Gachon University Of Industry-Academic Cooperation Foundation | Magnetic resonance imaging system |
CN109620224A (en) * | 2019-01-10 | 2019-04-16 | 哈尔滨华奥新技术开发有限公司 | Electron paramagnetic imager |
CN111505553A (en) * | 2019-07-12 | 2020-08-07 | 上海联影医疗科技有限公司 | Magnetic resonance imaging system and method |
CN111505553B (en) * | 2019-07-12 | 2023-07-11 | 上海联影医疗科技股份有限公司 | Magnetic resonance imaging system and method |
Also Published As
Publication number | Publication date |
---|---|
WO1990013047A1 (en) | 1990-11-01 |
CA2050494A1 (en) | 1990-10-25 |
NO914170L (en) | 1991-10-23 |
ATE108026T1 (en) | 1994-07-15 |
AU638985B2 (en) | 1993-07-15 |
DE69010329D1 (en) | 1994-08-04 |
CA2050494C (en) | 1999-09-07 |
DE69010329T2 (en) | 1994-10-20 |
JPH04506614A (en) | 1992-11-19 |
NO914170D0 (en) | 1991-10-23 |
AU5409990A (en) | 1990-11-16 |
NO302447B1 (en) | 1998-03-02 |
EP0470084B1 (en) | 1994-06-29 |
GB8909270D0 (en) | 1989-06-07 |
JP2902107B2 (en) | 1999-06-07 |
EP0470084A1 (en) | 1992-02-12 |
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